An object-sensing device is a device capable of sensing the presence of an object, and sometimes determines the location of the object on the device. Incorporation of object-sensing capability into display devices is becoming increasingly desirable, as it allows the display device itself to also be used as a user input device, eliminating the need for cumbersome components such as keyboards, keypads, and mouse. Using an object-sensing display device, a user can, for example, touch images of buttons on the display to make a selection or type a word. Object-sensing display devices can be useful for applications such as automatic telling machines (ATMs), mobile/cellular phones, and personal digital assistants (PDAs).
There are a few different types of object-sensing devices. A resistive-type touch sensing display device senses a current change in response to the touch. A surface-wave-type touch sensing display device senses a supersonic change in response to the touch. A radiation-sensing-type display device typically includes a radiation emitting element and a radiation receiving element and senses a change in the intensity of the radiation when an object is present compared to when no object is present.
While the radiation-sensing-type display device is advantageous because of its large object-sensing area, it is desirable to lower its manufacturing cost.